capture-console is a small Node.js library built to help when capturing log output via
process.stderr. The main use case is unit testing (which is why I built it), but there's no reason it can't be used in production code paths.
capture-console lives on npm, so just install it via the command line and you're good to go.
$ npm install --save-dev capture-console
There are a whole bunch of ways to use
capture-console, mainly due to scoping, with the two easiest defined below. Depending on your use case you might be pushed more towards one than the other, but in general you can just choose your preference.
The easiest way to use
capture-console is with scoping; this is when the output of a provided function is captured.
Note that this form assumes synchronous execution - async stuff will require manual hookups (below).
var capcon = ;var stderr = capcon;var stdout = capcon;var stdio = capcon;
There are also ways to manually stop and start a capture context, by passing a process stream to watch and a callback to fire on each message.
var capcon = ;// our buffervar output = '';// the first parameter here is the stream to capture, and the// second argument is the function receiving the outputcapcon;// whatever is done here has stdout captured - but note// that `output` is updated throughout executioncapcon;// anything logged here is no longer captured
You should be aware that all
capture functions will still pass the values through to the main stdio
write() functions, so logging will still go to your standard IO devices.
If this is not desirable, you can use the
intercept functions. These functions are literally
s/capture/intercept when compared to those shown above, and the only difference is that calls aren't forwarded through to the base implementation.